The West Carleton Amateur Radio Club
Dallas Semiconductor 1-Wire system Resource File
Including the 1-Wire Weather Station


The purpose of this file is to present links and other information to support the implementation of the Dallas 1-Wire system components for weather sensors and other types of instruments.


Dallas Semiconductor - Supplier of the 1-Wire components and weather station kits.  The basic weather station kit measures wind speed, wind direction, and the temperature inside the instrument.  Also available is a tipping-bucket type 1-Wire Rain Gauge.  These instruments are well made, and are a good value at the prices.  See below for links to the DS specification sheets and application notes.

Here is a threaded mail archive / discussion on the implementation of 1-Wire weather instruments  problems and solutions.

Point Six, Inc. offer a variety of 1-Wire sensors.  See the link below to the PSix application notes, which include hints for a successful 1-Wire network.

Here is one implementation of a Dallas 1-Wire weather station for APRS by Will, N0XGA, and Russ, KB0TVJ (wind direction and speed, plus temperature; they are thinking about barometric pressure).  The authors feed the output to a controller (Motorola 6808).  TAPR has a kit available.


Distributors of 1-Wire components

The weather station kits are available directly from Dallas Semiconductor in Dallas, Texas in the U.S.A.   Link to the DS Weather Station and Rain Gauge kits.  ( As of July 30th, 2000 Dallas is out of stock on the basic weather station kit.  Future availability from DS at the previous price is not known at present.  The rain gauge kit is still available.)

DS has announced the availability of a 1-Wire Relative Humidity module which can be ordered directly from DS, for $20 US.  See the DS iButton web site for details.

Another manufacturer has stepped into the breach ..... 
AAG - Automatización Aplicada a Gasolineras in Mexico is offering the same 1-Wire design as the Dallas kit, with some improvements such as coated electronics, a balanced wind direction rotor, and an interlocking case to help seal out moisture.   This kit includes the basic unit for wind speed and direction, plus temperature (inside the case).  Their price is the same as the kit was from Dallas - $79 US.  Many people will be pleased to see the return of this kit at a reasonable price.


 Distributors of Dallas 1-Wire electronic components in Canada are : 
Insight: 1-800-204-0010, and
Avnet: 1-800-408-8353.

In the Ottawa ON area, these distributors are at the following locations:

Insight
240 Catherine St.
Suite 405
OTTAWA, ON
Canada K2P 2G8
PH: (613) 2331799
FAX: (613) 2332843
.
Avnet
190 COLONNADE ROAD
NEPEAN, ON 
Canada K2E 7J5 
Mike Gardner, District Manager
613-226-1700
FAX: 613-226-1184
mike.gardner@avnet.com

For the locations of these distributors in other parts of Canada, please send me an Email.


Specifications and Application Notes.  These are Acrobat .pdf files.

Dallas Semiconductor Data Sheets and DS Application Notes -

Some of the the 1-Wire parts of particular interest are:

DS1820
DS2401
DS2406
DS2423
DS2438
DS2450
DS2890
Digital Thermometer
Silicon Serial Number
Dual-Addressable Switch
Counter
'Battery Monitor' (ADC)
Quad A/D Converter
Addressable Potentiometer

The DS2401 can be used to indicate whether a door or window alarm circuit in a 1-Wire network is open or closed, as an example.

See also the technical brief 'Microlan Design Guide' (html file) by Dan Awtrey, DS engineer.

Point Six Inc. Application Notes -  There is some very useful information here on implementing a 1-Wire micro Local Area Network.

Parallax has a new 'Super Stamp' processor, the Basic Stamp II Plus.   The BS II+ will support the Dallas iButton and 1-Wire systems, in addition to other features.  It comes in 24pin and 40pin (more I/O) versions.  Check the Parallax web site for details.  This controller should permit putting together an environmental monitoring station using a combination of DS 1-Wire and 'conventional' sensors.

Now here's a neat gadget - for designing a 1-Wire network with a microcontroller or with a PC - the Point Six HA7S - a TTL to 1-Wire Host Adapter.  This small 6-pin SIP module accepts ASCII commands, controls the 1-Wire bus, and provides a direct connection to a UART or microprocessor I/O.  It relieves the host of generating the time-critical 1-Wire waveforms and it will support all 1-W devices, up to 100 devices and up to 2000 feet of CAT. 5 twisted pairs cable.  Check the full description on the Point Six web site.  This is advertised at $28.95US each.  It looks pretty pricey at first glance, but it might permit the use of relatively slow controllers such as the Parallax Basic Stamp II for controlling a 1-Wire network - pretty handy too if you are not a whiz at programming in assembler or C.

Dallas Semiconductor has a nifty kit for the evaluation of the DS2450 quad analogue to digital converter.  This kit (the DS2450K) includes a circuit board, power supply, PC DB9 serial cable, PC software and a thermocouple.  The circuit board is intended to demonstrate real-time measurements of voltage (0-5V), current (0-20mA), ambient light level, temperature and external sensors.  The DS2450K has on (the circuit) board a DS2450 quad A/D convertor, a DS1820 digital thermometer, a DS2406 dual addressable switch, a DS275 line-powered RS-232 transceiver and an HA7S, PLUS a solid-state relay (140 VAC at 3 A ), plus a terminal block for connections to external components.  All this for $49.00US. 

On the DS2450K board, the four inputs to the DS2450 are set up as follows:

Channel A has an on-board photocell that measures ambient light.
Channel B is connected to an instrumentation amplifier for sensors and low-level signals.  The amplifier provides differential gain adjustable from 5V/V to 10,000 V/V.  This allows a full scale differential signal as small as 0.5 mV to be amplified to a level of 5 Volts, required to interface low level signals such as thermocouples, load cells, strain gauges and (some) pressure sensors.  Offset is adjustable on the DS2450K circuit board.
Channel C is connected to the external 0-5V input.
Channel D is set up to measure current of 0-20mA, a standard in common industrial use.

The software included with the DS2450K (runs under Windows 95/98) monitors the four analogue input channels of the DS2450, does real-time graphs of each channel, logs data from any channel, and has a built-in PID loop controller and graphing [Proportional (the comparative relation of setpoint to error) Integral (accumulated average of errors over time) Derivative (rate of change of errors over time)].


  Measuring Atmospheric Pressure

Here are two designs for measuring Atmospheric Pressure using the Motorola MPX4115 series of sensors and the DS2438 A/D converter.  In each case the output of the MPX4115 is scaled with an operational amplifier to expand the voltage range of interest for atmospheric pressure.  These use the DS2438 1-Wire ADC.

Design by David Bray
   Schematic diagram for the Bray barometer 

Design by Andrew G. Miller

This is a third design by Simon Atkin using a DS2760 rather than a 2438.  The circuit board design is shown, but no schematic information is available at present.

   Counting Lightning Strikes

Here is a design for a lightning detector using the Dallas Semiconductor 1-Wire technology at <http://www.timbitson.com/weather/owlm/index.html>.


- More information to follow -


Go to the Weather and Environmental Monitoring Introductory  Page. Go to the Notes and Links - Commercial and Kit Stations  Page. Go to the Notes and Links - Sensors Page.
Go to the West Carleton 
A R C Home Page.
Go to the WCARC 902-928 MHz Band Project Web Site. Send Email to me -
Graham Ide   VE3BYT

1KM